DE102013110951A1 - Mobile work machine with dual-circuit brake - Google Patents

Abstract

In a mobile work machine, in particular an industrial truck, with at least one brake, in which a brake rotor disk (6) to be braked is braked with non-rotating friction elements (7) which are actuated via a pressure piston (9) of at least one hydraulic cylinder (14), and the hydraulic cylinder (14) is connected to a brake actuating device via a first hydraulic brake circuit (12), a separating piston (15) in the pressure chamber of the hydraulic cylinder (14) separates a first working chamber (13) which is connected to the first hydraulic brake circuit (12). is connected, and a second working space (17) which is connected to a second hydraulic brake circuit (16), the separating piston (15) facing away from the pressure piston (9) against a stop (21) and is supported on the pressure piston (9) transmitted force of the separating piston (15) by a thrust element (19) on the pressure piston (9).

Description

The invention relates to a mobile machine with a dual-circuit brake. In particular, the invention relates to a mobile work machine, such as an industrial truck, with at least one brake in which a braked brake rotor disc is compressed for braking with non-rotating friction elements, which are actuated via a pressure piston at least one hydraulic cylinder, and the hydraulic cylinder with a brake actuator via a first hydraulic brake circuit is connected.

In mobile machines, especially industrial trucks, such as a forklift, braking devices are known, which are usually hydraulically controlled as a negative brake to allow a parking brake function. By spring preload, the brake closes automatically in the pressureless state of the hydraulic system, while for releasing the brake by the hydraulic system, such as by pressure cylinder, the spring tensioned and the brake is released.

One embodiment of such a brake is a multi-disc brake in which a package of a plurality of discs alternately has a stationary disc and a rotating disc. During braking, this package is compressed by means of fixed discs at the ends and decelerated over the entire grinding surface connected to the rotating discs shaft. An embodiment of such disk brakes is wet running and thus maintenance-free. Other embodiments of the actual brake, which were used in older mobile machines are, for example, outer jaw, drum or dry running full disc brakes.

It is also known to use this type of brakes, which have a parking brake function, as a service brake while driving the mobile machine. It must be possible to use the service brake dosed depending on the operation by the driver. This can be achieved by the release force of the parking brake is canceled dosed, for example, in a hydraulic pressure cylinder as the parking brake venting element via a pedal-operated pressure relief valve.

A disadvantage of this prior art is that especially in wet-running, spring-loaded multi-disc brakes, but also in the other enumerated types of brakes, the driver receives no feedback on the foot pedal or an actuator, from what time the brake, such as the slats at a multi-disc brake, because the entire system is a power brake system and the driver is controlled only the pressure of the lifting force. The actual brake pressure is generated by the spring force and does not lead to the driver to a force feedback on actuation of the brake pedal. This can lead to overbraking and to a load shedding, if, for example, a forklift as an industrial truck with a recorded load is slowed down so much that the load from the load receiving means, such as forks, slides. To improve this, for example, brake systems of industrial trucks, especially forklifts, are known in which the braking force for the service brake is generated by a separate pressure cylinder regardless of the spring force and not by controlling the release force. As a further variant it is known that the own pressure cylinder overcomes the release force and thereby generates a good controllable braking force.

For a possible operation on public roads a dual-circuit braking system of the service brake is required in accordance with the registration requirements, so that in case of failure of a brake circuit, the second brake circuit of this still works independently.

From the DE 10 2009 031 741 A1 a braking device for a mobile work machine is known, which can be used both as a service brake and as a parking brake. In this case, a biased by spring force multi-disc brake is released by hydraulic pressure and can be drained in a first brake circuit via an operating pedal and a brake valve, the hydraulic pressure for braking. In a second brake circuit via a pressure cylinder, an additional brake pressure acts on the lamella, which is generated by the foot pedal. Further, the document discloses an arrangement of three switching valves, one of which derives via a pressure relief device, the release pressure of the parking brake in the de-energized state. By this arrangement, an abrupt braking and thus a load shedding in case of power failure is avoided.

A disadvantage of this prior art is that for the one brake circuit still the disadvantages described above of the lack of feedback to the driver and by the always simultaneous operation of both brake circuits, the aforementioned disadvantages and effects occur.

It is also known, in a forklift, a cone brake in which conical surfaces are pressed together by an axial shoe movement to use as a service brake, which can be very compact and compared to other types of brakes, such as an external shoe brake, a gain factor has, so that even in a non-power-assisted operation alone by the foot force of a driver, a sufficiently large braking force can be achieved. From the DE 34 17 271 A1 is known a cone brake, which is used in a forklift. From the DE 29 39 825 A1 is known a friction brake for braking industrial trucks and in particular a forklift, which has a cone brake in one embodiment.

In electrically operated trucks having electric traction motors whose energy is obtained from a traction battery, it is possible to arrange the brake assemblies described above together with one traction motor for each drive wheel in a compact axis.

The present invention has for its object to provide a mobile machine with an improved brake available, which avoids the disadvantages mentioned above and a compact design of a dual-circuit brake system for a mobile machine, in particular a forklift truck as an industrial vehicle allows.

This object is achieved by a mobile machine with the features of independent claim 1. Advantageous developments of the invention are specified in the subclaims.

The object is achieved in that in a mobile machine, in particular a truck, with at least one brake in which a braked brake rotor disc is compressed to decelerate with non-rotating friction elements, which are actuated via a pressure piston at least one hydraulic cylinder, and the hydraulic cylinder with a brake actuating device is connected via a first hydraulic brake circuit, a separating piston in the pressure chamber of the hydraulic cylinder a first working space, which is connected to the first hydraulic brake circuit, and a second working space, which is connected to a second hydraulic brake circuit separates and the separating piston of facing away from the plunger against a stop and a directed to the pressure piston force of the separating piston is transmitted by a thrust element on the pressure piston.

When pressing the brake actuator, the driver advantageously receives a feedback on the applied braking force, in particular he notices the beginning of braking when the friction engage the brake rotor disk, as in any of the two hydraulic brake circuits, the operation of a release of pressure of the air Parking brake depends. This results in a well-to-dose and sensitively operated service brake, which is constructed very compact at the same time with two hydraulic brake circuit. The arrangement of an additional separating piston a single hydraulic cylinder is sufficient, resulting in a very compact and inexpensive construction. At the same time it is still possible to completely separate the two hydraulic brake circuits in their function. Mobile machines and especially industrial trucks often have only low speeds and only one driven axle, which is also braked alone and as a single axis. The arrangement of a separating piston redundancy of the brake system can be achieved without significant additional construction costs or installation space for the brake system is required. In this case, the control of the brake system via a foot pedal can be done as a brake actuator, which directly actuates a master cylinder and / or also applied via a control valve means the brake with pressure. In this case, the elasticity of a sealing ring can be utilized as the return force for the printing cylinder. Alternatively or additionally, a return spring can also be provided if necessary.

If in the second working space, which is assigned to the side facing away from the pressure piston side of the separating piston, due to a malfunction, such as a leak, no pressure is built up, the separating piston is pushed away from the plunger to the stop. The stop may be a gradation in the hydraulic cylinder or an extra component inserted for this purpose. The separating piston, which preferably has a seal relative to the hydraulic cylinder, then allows the build-up of pressure in the first working space, so that the pressure piston can continue to perform its function and presses the friction elements to the brake rotor disc, so that the brake rotor disc is decelerated. Conversely, if there is a pressure drop in the first working space due to a malfunction, the separating piston is pushed by the pressure in the second working space on the pressure piston back. By means of a thrust element located in the first working space, which may for example also be a separate, longitudinally rigid component guided in the hydraulic cylinder, the pressure force of the separating piston is transmitted to the pressure piston and it is ensured that the friction elements continue to be pressed against the brake rotor disk. In this case, the pressure piston may be formed as a separate component or else integrally with a carrier component for friction linings, or the friction elements, for example with an axially displaceable stator disk.

Advantageously, the thrust element is a rod connected to the separating piston, in particular a rod arranged in an axis of the separating piston.

If the separating piston is integrally formed with a corresponding rod, then this can be easily and inexpensively produced as a rotating part, for example. The thrust element is guided by the separating piston itself in the hydraulic cylinder.

The stop may be an inserted into a groove retaining ring.

As a result, the stop can be formed in a very cost-effective manner. In particular, the hydraulic cylinder can be designed in a single through hole, since the corresponding groove for the retaining ring can be added later.

In one embodiment, the pressure piston presses a stator disk as a non-rotating friction element against the brake rotor.

Through the stator, a full-surface brake can be implemented with the brake rotor disk. Although the brake rotor disk is provided so as to be axially displaceable on its rotating shaft, the brake rotor disk can be pressed by the stator disk against a likewise fixed braking surface, for example in a housing, so that the brake rotor disk is braked on both sides.

Advantageously, the pressure piston is arranged in an axis of the stator.

By this symmetrical arrangement only a single hydraulic cylinder is required. Otherwise, several hydraulic cylinders would have to be distributed symmetrically over the circumference to achieve a uniform compressive force.

In a further development of the mobile working machine, the brake rotor disk and the stator disk have corresponding cones on each other.

A brake cone or a conical shape of the braking surfaces leads to a reinforcing effect and thus can be achieved even with a brake that is not composed of several discs and is operated only by foot force, a sufficient braking effect. Also, in such a cone brake, the complexity of the brake system is significantly lower than, for example, in a multi-disc brake with a plurality of brake rotor discs and stator discs. This results in lower costs.

Advantageously, the mobile work machine having a drive axle, in each of which a drive wheel associated with a drive motor, in particular an electric drive motor, and each one each drive motor associated brake are integrated.

Especially in electrically driven industrial trucks as an example of a mobile work machine in which a separate electric motor is provided for each drive wheel on each side of the vehicle, which is supplied from a traction battery with electrical energy, such a compact construction of a drive axle. In this drive axle, an electric motor and a brake for the respective drive wheel are then integrated on each side. The possibility of a compact construction is particularly advantageous. Since these trucks usually have just a single, provided with brakes, drive axle, the possibility is particularly advantageous to provide a dual-circuit hydraulic brake in this compact design. This is especially true if the vehicle is to be moved on public roads and must comply with the relevant registration requirements.

In a favorable embodiment, the brakes in the drive axle can be arranged inside such that the respective hydraulic cylinders are in alignment and the second working spaces of the hydraulic cylinders form a common working space.

This allows for further simplification by allowing the hydraulic cylinder to be formed by a single through bore for the brakes on both sides. The common working space is then arranged in the middle, for example in the middle of the drive axle.

Advantageously, the first hydraulic brake circuit and the second hydraulic brake circuit with a tandem master cylinder of the brake operating device, in particular a foot pedal connected.

Tandem master cylinder are available as supplier parts from the automotive sector cost and in various embodiments available. Through this, a complete separation and control of the two brake circuits via the brake actuator can be achieved in a simple manner. If leakage occurs in one of the brake circuits, the mobile working machine can still be decelerated in doses via the other brake circuit. The braking forces which occur in the event of a brake circuit failure are furthermore symmetrical with respect to the two sides of a vehicle and it is possible to avoid breaking away from the lane and / or lane loss of the vehicle.

In a further embodiment, the brake can also act as a parking brake by the brake rotor disc and the friction elements are biased by at least one spring in the braking position and can be released by a ventilation device.

For the aforementioned applications, especially trucks, it is particularly advantageous if the parking brake is integrated into the compact construction of the brake. This makes it possible to integrate the parking brake in the overall arrangement of the drive axle.

The ventilation device may be a hydraulic ventilation device which is connected to a parking brake valve device, wherein the parking brake valve device has a first electrically actuated switching valve which has an active blocking position and an electrically switchable, a pressure chamber of the hydraulic airing device with a pressure supply device connecting pressure build-up position in the de-energized state.

About this electrically actuated switching valve, the parking brake can be solved not only on a control command of a driver, but also automated. This allows automated actuation of the parking brake.

In one embodiment, the parking brake valve device has a second electrically actuable switching valve which has a blocking position which is effective in the de-energized state and an electrically switchable pressure-free position which connects the pressure chamber of the hydraulic ventilating device with a pressure sink.

As a result, the parking brake can also be solved automatically, since it can be electrically switched.

The parking brake valve device may comprise a third electrically actuatable switching valve which has an effective in the de-energized state, the pressure chamber of the hydraulic release device with a pressure reduction device connecting pressure reduction position and an electrically switchable blocking position.

If the parking brake valve device unexpectedly de-energized, such as in an electrically operated mobile work machine with a disruption of the power supply from the traction battery, the pressure of the hydraulic release is delayed and slowly degraded. This prevents overbraking and load shedding resulting from this overbraking, for example in the case of a forklift truck driving with an overlying load.

Advantageously, the mobile work machine is an industrial truck, in particular a counterbalance forklift.

A further advantage is that can be braked in the fork lift truck failure of a brake circuit without loss of track.

In industrial trucks, especially counterbalance forklifts, the brake described is particularly advantageous because they usually have only a driven and braked front drive axle directly on the mast and the rear, arranged under the counterweight steered wheels are neither driven nor have brakes.

Further advantages and details of the invention will be explained in more detail with reference to the embodiments illustrated in FIGS. This shows the

1 1 is a partial sectional view of a drive axle of a mobile machine with a dual-circuit brake,

2 in perspective, the parking brake from the 1 and

3 schematically a partial section of a drive axle of a mobile machine with a further embodiment of a dual-circuit brake.

The 1 schematically shows a partial section of a drive axle 1 a counterweight forklift, not shown as an example of a truck or a mobile machine. In an axle housing 2 are a first electric motor 3 and a second electric motor 4 arranged, each over a shaft 5 with a brake rotor disk 6 interact and drive not shown drive wheels. The brake rotor disc 6 can each with a stator disk 7 as a friction element 8th by a respective pressure piston 9 be compressed.

A foot pedal 10 acts with a tandem master cylinder 11 together, via a first hydraulic brake circuit 12 each with a first work space 13 a common for both brakes hydraulic cylinder 14 connected is. The first workroom 13 lies in the common hydraulic cylinder 14 while on the respective pressure piston 9 facing side of a separating piston 15 , From the tandem master cylinder 11 leads a second hydraulic brake circuit 16 to a common second workspace 17 in the hydraulic cylinder 14 passing through the respective separating piston 15 opposite the respective pressure piston 9 is separated and in the middle of the drive axle 2 lies.

The separating pistons 15 each have a pole 18 as a pushing element 19 on, through the one on the separating piston 15 by the pressure in the second working space 17 applied force respectively to the pressure piston 9 is transferred, even if the first work space 13 due to a malfunction has no pressure. If, conversely, in the common second working space 17 due to a malfunction no pressure is applied, so come the separating piston 15 by the pressure in the respective first work spaces 13 in the position shown, in which they on a respective retaining ring 20 as a respective stop 21 issue. This can increase the pressure in the first work space 13 build up so far that this one force on the pressure piston 9 continues to exercise and the stator disc 7 against the brake rotor disc 6 suppressed. Also in case of failure of a brake circuit 12 . 16 can still be braked dosable. In case of failure, the drive wheels on both sides of the vehicle are still braked with the same force without leaving the lane.

The friction elements 8th have a brake cone as a friction surface 22 up, with a corresponding counter-cone 23 the brake rotor disk 6 works together. The interaction of brake cone 22 and counter-cone 23 causes axial displacement of the stator disk 6 a high surface pressure and thus a reinforcing effect. This can be achieved in a compact space even without the multiple discs of a multi-disc brake high braking performance.

In the axle housing 2 is still a parking brake 24 integrated, consisting of a ring piston 25 as a ventilation device 26 in a ring cylinder 27 consists. By several distributed over the circumference springs 28 becomes the stator disk 7 on the brake rotor disc 6 biased and when applying a hydraulic pressure through the annular piston 25 ventilated. The respective ring pistons 25 are via a hydraulic line 29 with a parking brake valve device 30 connected to the respective ring piston 25 three electrically actuated switching valves S1, S2, S3 upstream, which are preferably designed as seat valves.

The first switching valve S1 is in the de-energized state in a blocking position and has an electrically switchable pressure build-up position, in which the annular piston 25 with a pressure supply device 31 are connected, for example, a pressure medium pump. The second switching valve S2 is in the de-energized state also in a blocking position and has an electrically switchable, the annular piston 25 with a tank 32 connecting pressure release on. The third switching valve S3 connects in the de-energized state, a pressure reduction position, the annular piston 25 with a pressure reduction device, for example as a pressure valve 33 is formed, and can be electrically switched to a blocking position.

When de-energized second switching valve S2, the connection of the annular piston 25 to the pressure sink, ie to the tank 32 , interrupted and it can by energizing the first and third switching valve S1, S3, the annular piston 25 acted upon hydraulically and thereby one of the spring force opposite force can be generated. This will make the springs 28 compressed and the parking brakes 24 solved.

The parking brake 24 can be closed in the sense of an automatic parking brake when first the first and third switching valve S1, S3 are no longer energized and a short time after the second switching valve S2 is energized. The switching valve S2 ensures an immediate pressure reduction in the annular piston 25 the spring-loaded brakes 24 so the springs 28 the parking brakes 24 shut down.

If a power failure occurs in the mobile work machine, all switching valves S1, S2, S3 are de-energized. The first and second switching valve S1, S2 thus switch in blocking position and the third switching valve S3 in the pressure reduction position, in the time-delayed pressure reduction in the annular piston 25 the parking brakes 24 close them first with a reduced braking torque.

When the parking brake 24 is manually engaged by the driver, S1 is de-energized and S2 energized. The parking brakes 24 then fall in immediately.

For the towing operation, the third switching valve S3 can be closed by hand and by a hand pump 34 Pressure in the ring piston 25 being constructed.

The 2 shows in perspective the parking brake 24 from the 1 , in the ring cylinder 27 is the ring piston 25 guided by the springs 28 in the direction of the stator disc 7 is biased. At the same time, the compressive force of the springs becomes 28 by plunger 35 transmitted through holes in a flange cover 36 are guided, the ring piston 25 seals. Between flange cover 36 and ring pistons 35 is through the hydraulic line 29 in the 1 Pressure medium supplied to the springs 28 to compress and the parking brake 24 to ventilate.

The 3 schematically shows a partial section of the drive axle 1 a mobile machine of a not shown Counterbalance forklift as an example of a truck or a mobile machine with a further embodiment of a dual-circuit brake. In the axle housing 2 are the first electric motor 3 and the second electric motor 4 arranged, each above the shaft 5 with the brake rotor disk 6 interact and drive the drive wheels, not shown. The brake rotor disc 6 can each with the stator disc 7 as a friction element 8th through each of the pressure piston 9 be compressed.

The foot pedal 10 acts with the tandem master cylinder 11 together, over the first hydraulic brake circuit 12 each with the first working space 13 of common for both brakes hydraulic cylinder 14 connected is. The first workroom 13 lies in the common hydraulic cylinder 14 while on the respective pressure piston 9 facing side of the separating piston 15 , From the tandem master cylinder 11 leads the second hydraulic brake circuit 16 to the common second workspace 17 in the hydraulic cylinder 14 passing through the respective separating piston 15 opposite the respective pressure piston 9 is separated and in the middle of the drive axle 2 lies. The separating pistons 15 each have the rod 18 as the pushing element 19 on.

The brake rotor disc 6 has friction linings in this embodiment 40 up and is on the wave 5 as well as the stator disc 7 slidably mounted. When through the pressure piston 9 the stator disc 7 on the brake rotor disc 6 is pressed, is also the brake rotor disk 6 moved and against a contact surface 41 in the axle housing 2 pressed. This will make the brake rotor disc 6 slowed down on both sides by frictional forces.

In the axle housing 2 is still the parking brake 24 integrated, which from the ring piston 25 as the ventilation device 26 in the ring cylinder 27 consists. Through the several circumferentially distributed springs 28 becomes the stator disk 7 on the brake rotor disc 6 biased and when applying a hydraulic pressure through the annular piston 25 ventilated. The respective ring pistons 25 are over the hydraulic line 29 with the parking brake valve device 30 connected to the respective ring piston 25 the three electrically actuated switching valves S1, S2, S3 upstream, which are preferably designed as seat valves.

The first switching valve S1 is in the de-energized state in a blocking position and has an electrically switchable pressure build-up position, in which the annular piston 25 with the pressure supply device 31 are connected, for example, a pressure medium pump. The second switching valve S2 is in the de-energized state also in a blocking position and has an electrically switchable, the annular piston 25 with the tank 32 connecting pressure release on. The third switching valve S3 connects in the de-energized state, a pressure reduction position, the annular piston 25 with a pressure reduction device, for example as a pressure valve 33 is formed, and can be electrically switched to a blocking position.

When de-energized second switching valve S2, the connection of the annular piston 25 to the pressure sink, ie to the tank 32 interrupted and it can by energizing the first and third switching valve S1, S3, the annular piston 25 acted upon hydraulically and thereby one of the spring force opposite force can be generated. This will make the springs 28 compressed and the parking brakes 24 solved.

The parking brake 24 can be closed in the sense of an automatic parking brake when first the first and third switching valve S1, S3 are no longer energized and a short time after the second switching valve S2 is energized. The switching valve S2 ensures an immediate pressure reduction in the annular piston 25 the spring-loaded brakes 24 so the springs 28 the parking brakes 24 shut down.

If a power failure occurs in the mobile work machine, all switching valves S1, S2, S3 are de-energized. The first and second switching valve S1, S2 thus switch in blocking position and the third switching valve S3 in the pressure reduction position, in the time-delayed pressure reduction in the annular piston 25 the parking brakes 24 close them first with a reduced braking torque.

When the parking brake 24 is manually engaged by the driver, S1 is de-energized and S2 energized. The parking brakes 24 then fall in immediately

For the towing operation, the third switching valve S3 can be closed by hand and by the hand pump 34 Pressure in the ring piston 25 being constructed.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009031741 A1 [0007]
• DE 3417271 A1 [0009]
• DE 2939825 A1 [0009]

Claims (14)

Mobile work machine, in particular industrial truck, with at least one brake, in which a brake rotor disk to be braked ( 6 ) for braking with non-rotating friction elements ( 7 ) is compressed, which via a pressure piston ( 9 ) at least one hydraulic cylinder ( 14 ) and the hydraulic cylinder ( 14 ) with a brake actuating device via a first hydraulic brake circuit ( 12 ), characterized in that a separating piston ( 15 ) in the pressure chamber of the hydraulic cylinder ( 14 ) a first work space ( 13 ) connected to the first hydraulic brake circuit ( 12 ) and a second workspace ( 17 ), which is connected to a second hydraulic brake circuit ( 16 ), separates and the separating piston ( 15 ) from the pressure piston ( 9 ) facing away from a stop ( 21 ) and one on the pressure piston ( 9 ) directed force of the separating piston ( 15 ) by a pushing element ( 19 ) on the pressure piston ( 9 ) is transmitted. Mobile working machine according to claim 1, characterized in that the pushing element ( 19 ) one with the separating piston ( 15 ) connected rod ( 18 ), in particular one in an axis of the separating piston ( 15 ) arranged rod ( 18 ). Mobile work machine according to claim 1 or 2, characterized in that the stop ( 21 ) an inserted into a groove retaining ring ( 20 ). Mobile work machine according to one of claims 1 to 3, characterized in that the pressure piston ( 9 ) a stator disk ( 7 ) as a non-rotating friction element ( 8th ) against the brake rotor disc ( 6 ) presses. Mobile work machine according to claim 4, characterized in that the pressure piston ( 9 ) in one axis of the stator disk ( 7 ) is arranged. Mobile work machine according to claim 5 or 6, characterized in that the brake rotor disk ( 6 ) and the stator disc ( 7 ) have corresponding cone. Mobile work machine according to one of claims 1 to 6, characterized in that the mobile working machine a drive axle ( 1 ), in each of which a drive wheel associated with a drive motor, in particular an electric drive motor ( 3 . 4 ), and each one associated with each drive motor brake are integrated. Mobile work machine according to claim 7, characterized in that the brakes in the drive axle ( 1 ) are arranged inside such that the respective hydraulic cylinders ( 14 ) and the second workrooms ( 17 ) of the hydraulic cylinders ( 14 ) a common working space ( 17 ) form. Mobile work machine according to one of claims 1 to 8, characterized in that the first hydraulic brake circuit ( 12 ) and the second hydraulic brake circuit ( 16 ) with a tandem master cylinder ( 11 ) of the brake actuating device, in particular a foot pedal ( 10 ), connected is. Mobile work machine according to one of claims 1 to 9, characterized in that the brake as a parking brake ( 24 ) can act by the brake rotor disc ( 6 ) and the friction elements ( 8th ) by at least one spring ( 28 ) are biased in the braking position and can be ventilated by a ventilation device. Mobile work machine according to claim 10, characterized in that the ventilation device is a hydraulic airing device which is provided with a parking brake valve device ( 30 ), wherein the parking brake valve device ( 30 ) has a first electrically actuable switching valve (S1), which in the de-energized state, an effective blocking position and an electrically switchable, a pressure chamber of the hydraulic ventilation device with a pressure supply device ( 31 ) has connecting pressure build-up position. Mobile work machine according to claim 11, characterized in that the parking brake valve device ( 30 ) has a second electrically actuated switching valve (S2), which has an effective in the de-energized state blocking position and an electrically switchable, the pressure chamber of the hydraulic release device with a pressure sink ( 32 ) has connecting depressurization. Mobile work machine according to claim 11 or 12, characterized in that the parking brake valve device ( 30 ) comprises a third electrically actuable switching valve (S3) which has an effective in the de-energized state, the pressure chamber of the hydraulic release device with a pressure reducing device ( 33 ) has connecting pressure reduction position and an electrically switchable blocking position. Mobile work machine according to one of claims 1 to 13, characterized in that the mobile work machine is an industrial truck, in particular a counterbalance forklift.

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